Improved albedo formulation for chemistry transport models based on satellite observations and assimilated snow data and its impact on tropospheric photochemistry

T. Laepple, M. G. Schultz, J. F. Lamarque, S. Madronich, R. E. Shetter, B. L. Lefer, Elliot L Atlas

Research output: Contribution to journalArticle

10 Citations (Scopus)

Abstract

Present parameterizations of the UV surface albedo in global chemistry transport models are generally based on a crude land cover classification and do not account for interannual variations of the snow-covered surface or the large variability in the albedo of snow-covered surfaces. We developed an improved scheme based on 2 years of Moderate-Resolution Imaging Spectroradiometer (MODIS) albedo data, a fine-resolution MODIS land cover map, Global Ozone Monitoring Experiment (GOME) albedo data, and daily assimilated snow cover maps from the European Centre for Medium-Range Weather Forecasts or the National Centers for Environmental Prediction. The new parameterization improves the calculation of photolysis frequencies in particular in the subarctic region as shown by a comparison of the calculated ratio of upwelling and downwelling actinic fluxes with spectral measurements from the Tropospheric Ozone Production About Spring Equinox (TOPSE) campaign (January-May 2000). The impact of surface albedo changes on tropospheric photochemistry has been investigated using the global MOZART-2 chemistry transport model. Compared with the original model version, the surface albedo changes alter the tropospheric oxidizing capacity (OH concentrations) between -20 and +200% locally and +5% in the global annual mean. About half of this change results from a new value adapted for the ocean UV albedo. Locally, NOx concentrations were found to decrease by up to 40% and were most pronounced where the snow boundary crosses the high-emission regions in Europe, North America, and Asia. The interannual variability of snow and sea ice cover can lead to changes in the global tropospheric OH-concentration of 0.5%, which is of similar magnitude compared with the impacts of varying water vapor, transport, ozone column, and emissions as discussed in previous studies.

Original languageEnglish (US)
Pages (from-to)1-12
Number of pages12
JournalJournal of Geophysical Research C: Oceans
Volume110
Issue number11
DOIs
StatePublished - Jun 16 2005

Fingerprint

Photochemical reactions
satellite observation
photochemistry
snow
Snow
albedo
photochemical reactions
Satellites
chemistry
Ozone
formulations
Parameterization
ozone
MODIS (radiometry)
parameterization
Imaging techniques
MODIS
subarctic regions
Sea ice
land cover

ASJC Scopus subject areas

  • Oceanography
  • Astronomy and Astrophysics
  • Atmospheric Science
  • Space and Planetary Science
  • Earth and Planetary Sciences (miscellaneous)
  • Geophysics
  • Geochemistry and Petrology

Cite this

Improved albedo formulation for chemistry transport models based on satellite observations and assimilated snow data and its impact on tropospheric photochemistry. / Laepple, T.; Schultz, M. G.; Lamarque, J. F.; Madronich, S.; Shetter, R. E.; Lefer, B. L.; Atlas, Elliot L.

In: Journal of Geophysical Research C: Oceans, Vol. 110, No. 11, 16.06.2005, p. 1-12.

Research output: Contribution to journalArticle

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abstract = "Present parameterizations of the UV surface albedo in global chemistry transport models are generally based on a crude land cover classification and do not account for interannual variations of the snow-covered surface or the large variability in the albedo of snow-covered surfaces. We developed an improved scheme based on 2 years of Moderate-Resolution Imaging Spectroradiometer (MODIS) albedo data, a fine-resolution MODIS land cover map, Global Ozone Monitoring Experiment (GOME) albedo data, and daily assimilated snow cover maps from the European Centre for Medium-Range Weather Forecasts or the National Centers for Environmental Prediction. The new parameterization improves the calculation of photolysis frequencies in particular in the subarctic region as shown by a comparison of the calculated ratio of upwelling and downwelling actinic fluxes with spectral measurements from the Tropospheric Ozone Production About Spring Equinox (TOPSE) campaign (January-May 2000). The impact of surface albedo changes on tropospheric photochemistry has been investigated using the global MOZART-2 chemistry transport model. Compared with the original model version, the surface albedo changes alter the tropospheric oxidizing capacity (OH concentrations) between -20 and +200{\%} locally and +5{\%} in the global annual mean. About half of this change results from a new value adapted for the ocean UV albedo. Locally, NOx concentrations were found to decrease by up to 40{\%} and were most pronounced where the snow boundary crosses the high-emission regions in Europe, North America, and Asia. The interannual variability of snow and sea ice cover can lead to changes in the global tropospheric OH-concentration of 0.5{\%}, which is of similar magnitude compared with the impacts of varying water vapor, transport, ozone column, and emissions as discussed in previous studies.",
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AU - Atlas, Elliot L

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